The present invention relates to an expandable chute structure for throwing snow away from the road, to be incorporated in a snow plough vehicle such as a snow loader.
According to the conventional snow loader, a snow discharge opening of the chute is positioned as high as possible, and the chute is slantingly oriented upwardly in order to effectively enlarge the flying distance of the snow. Further, the chute must provide excellent rectification of snow flow therein by reducing resistivity against snow piece flow, and provide excellent convergence thereof.
Generally, the external size of the vehicle is defined by laws, and regulations, so that the chute having a high positional discharge opening must be retractable. In this case, during the operative state, the chute is telescopically expanded in order to heighten the position of the discharge opening, to thereby enhance snow-removing efficiency, while during the non-operative state (for mere running of the vehicle in out of service) the chute is retracted to meet with the vehicle height laws. Such an expandable structure has an additional advantage since when the vehicle is run in the non-operative state, the retracted chute widens the field of front vision for the operator. In other words, if the chute is a stationary structure, the chute may interrupt the view of field.
One of the conventional chute structures incorporated in the snow loader is shown in FIGS. 1 to 3(b), wherein a frame 6 is disposed in front of an operator's room 5. Mounted on the frame 6 are an auger 2 for levelling the snow, a blade 3 and a blower 4. The frame is vertically movable in accordance with the snow fall level.
Thus, as shown in FIG. 2, when the loader is advanced frontwardly with the blade 3 in the descent position in the snow surface, the snow scratched up by the blade 3 is compressingly gathered at the central portion thereof by the rotation of spiral members fixedly secured to a rotary shaft through an arm (not shown). The compressingly gathered snow is urged into an inlet opening 4a of the blower 4 opened at the central position of the blade 3. Thereafter, the snow is sucked into a water-wheel type centrifugal blower 4, broken into snow pieces, and the pieces are upwardly blown from a discharge opening 4b (FIG. 3a). The upwardly directed snow pieces are then introduced into a chute apparatus 1 through a chute 7 having one end confronted with the discharge opening 4b. The discharge opening 4b can be offset from the opening of the chute 7 by rotating a blower casing about its axis as illustrated by a dotted chain line in FIG. 3a. In this case, the snow pieces are directly discharged toward the atmosphere without passing through the chute apparatus 1. That is, the snow pieces are directly discharged toward the one lateral side of the snow loader and the snow pieces are diffusingly discharged, since the snow pieces are not subject to rectification.
The chute apparatus 1 includes a first frusto-conical duct 9 fixedly mounted on a chute table 8, a second duct 10 having its shape the same as that of the duct 9 and telescopically mounted thereon, and a main duct 11 having an arcuate shape telescopically mounted on the second duct 10. The main duct 11 has its base portion connected to a hydraulic cylinder 13 permitting vertical movement thereof. The vertical movement is guided by a guiding means 12 secured to the chute table 8. Therefore, upon completion of the retraction of a cylinder rod of the hydraulic cylinder 13, a chute opening 11a is positioned at the lowermost position as shown in FIGS. 2 and 3a, wherein the ducts 10 and 11 are superimposed with the duct 9. On the other hand, upon completion of the expansion of the cylinder rod, the chute opening 11a is at the uppermost position as shown in FIG. 3b, wherein the ducts 9, 10 and 11 are longitudinally aligned with one another to provide a telescopically expanded state. The direction of the chute opening 11a can be changed in a horizontal plane by rotating the chute table 8 about its vertical axis.
According to the conventional expandable chute apparatus 1, the vertical position of the chute opening 11a can be maintained high during snow-blowing operation. However, it is difficult to provide excellent rectification efficiency of the snow stream. To be more specific, the snow stream may be stalled within the ducts, and the snow pieces may be diffused during snow-throwing operation.
This disadvantage is due to the structure of the ducts. That is, the snow stream is generally rectified by the arcuate snow path. According to the conventional structure, the snow stream is extremely decelerated at its upward path defined by the first and second ducts 9, 10 prior to the snow reaching the inlet opening of the arcuate main duct 11. The decelerated snow stream strikes the inner peripheral surface of the main duct 11. The resulting snow speed is insufficient to provide excellent rectification efficiency. Further, the arcuate length of the main duct 11 is insufficient to provide a desirable rectification efficiency of the snow stream.
In order to overcome these drawbacks, another proposal has been made, wherein the inclination of the main duct 11 is increased with respect to the vertical direction to laterally direct the snow path thus allowing an enlarged arcuate length of the main duct. However, with this structure, flow resistivity is increased thus decreasing the flow speed of the snow, which in turn degrades the rectification efficiency of the snow stream.